A DC voltage conversion circuit is mounted on an apparatus which requires a stable DC voltage, and an apparatus which requires different DC voltage from a primary power supply. For example, in an apparatus, such as an electric vehicle, a satellite, which mounts a secondary battery and operates by DC, a switching-type DC voltage conversion circuit is used in order to stabilize a power source voltage which fluctuates depending on battery residue amount and obtain DC voltage necessary for load. In such a switching power supply, it is required to suppress the fluctuation of voltage and the like, while reducing size of passive components for miniaturization.
The switching power supply obtains a DC voltage, which is different from an input, by switching voltage and current using a switching device such as a semiconductor and smoothing using an inductor and a capacitor. In order to obtain a low ripple voltage and current, it is necessary to enlarge a value of an inductor or a capacitor, and the size of switching power supply is regulated by the size of these components.
On the other hand, there is known a technology of canceling ripple current by operating in parallel plural switching power supply circuits which operate with different phases mutually. According to this technology, even if the ripple current of each switching power supply circuit is large, in the whole apparatus, ripple current is canceled and the ripple of total current can be made small.
PLT 1 and PLT 2 disclose a technology which makes generated ripple current itself small by coupling magnetically plural switching power supply circuits which operate with different phases. According to these technologies, an inductor smaller than the conventional switching power supply circuit can be used, and the miniaturization of apparatus can be achieved.